1. Field of Invention
The present invention relates to a construction laser, and more specifically, a rotating construction laser having a rotating deflector mounted in a housing, where the rotating deflector is tiltable about two axes relative to the housing.
2. Description of Prior Art
Rotating construction lasers with a laser beam that rotates at least by segments are used, above all, in the construction industry to determine horizontal or vertical planes on walls, ceilings and floors or planes at defined inclinations on walls, ceilings and floors.
Conventional rotating lasers comprise a platform which is tiltable in two axes and on which the position sensing arrangement and rotating head are located. The rotating head is precisely adjusted relative to this sensing arrangement to several angular seconds. By means of actuating drives such as stepper motors that are fixed to the outer housing, this platform can be tilted relative to the housing in two directions by several angular degrees. Bubble levels are used as position sensors, and are read out optically by means of charge-coupled device (CCD) arrays or with photodiodes. A controlling device reads out these sensors for the x-direction and y-direction and moves the stepper motors in the appropriate direction until the air bubble of the bubble level is in the calibrated center position.
The stepper motors are usually geared down by pretensioned worm gear units to achieve the necessary angular accuracy. In this construction, the structural size, the weight of the stepper motors and the costs of the construction are disadvantageous. Further, the worm gear units can jam at the two end stops. The fact that the drive must be geared down very sharply can lead to mechanical self-locking at the mechanical end stops. When the stepper motor moves to this end stop, the worm is locked. The motor torque is then insufficient for freeing the gear unit from this self-locking.
According to DE 4406914, a self-leveling rotating construction laser has a laser unit that is arranged in a mounting frame, and whose laser beam can be deflected by approximately 90° by deflecting means, which are supported in a rotating part so as to be rotatable around an axis of rotation.
According to EP854351, the plane of rotation of the laser beam is tiltable in two swiveling planes extending perpendicular to one another. A rotational pin, which is supported so as to be tiltable in a universal ball joint bearing in the mounting frame, is tilted along with the laser unit and deflecting means by two actuating drives relative to the housing that is usually oriented horizontally. The actuating drives that are used, with their stepper motors and self-locking threaded spindles, have a complex construction and are prone to malfunctions.
According to DD291141, an electrooptical leveling instrument has a leveling telescope that is mounted in a rotatable underpart so as to be tiltable. The tilting of the leveling telescope with respect to the underpart is carried out by means of a piezo actuator that is connected to control electronics so as to be controllable.
In addition, piezo actuators are frequently used as an actuating drive according to DE3412014C1, DE19817802A1, EP1142039B1, e.g., for hexapods according to DE19742205A1, as a frictional-force drive in inertia slides according to EP360975A2, EP0799502B1, or as a dither motor apparatus for a laser gyroscope according to U.S. Pat. No. 4,987,334. In addition, according to the technical article by James Fried, et al., IEEE/ASME Transactions on Mechatronics, Vol. 9, No. 3, September 2004, different oscillation patterns can be generated depending on the control frequency with an individual, geometrically complex piezo actuator structure.